The present invention relates to a Coanda injector, in particular for cleaning filter elements of dust-laden gas filters, and includes an inlet for a medium to be suctioned, a pre-chamber having at least one inlet for a pressurized medium that can be supplied via a compressed gas line and having a preferably annular nozzle slot, and an outlet for the medium to be suctioned and the pressurized medium. The invention furthermore concerns a compressed gas line for connecting such a Coanda injector.
The Coanda Effect, named for the Romanian engineer and aviation pioneer Henri Coanda, describes the property of free streams of fluid of small cross-section to conform to adjacent physical surfaces and also to follow severe changes in course of the surface contour without detaching. By feeding a small quantity of a pressurized medium, i.e., a medium with increased pressure, Coanda injectors produce a high-volume media flow of lower pressure, generally approximately ambient pressure, in accordance with the Coanda effect. The media are air, nitrogen, and other gases conventionally employed in industry.
The areas of application for Coanda injectors are extremely varied. For instance, they are used in industry to cool machine elementsxe2x80x94such as motors and gearsxe2x80x94and electrical switching elements, for suctioning gases and dusts that occur in industry, for transporting warm air, steam or liquid, for drying, for loosening accumulations of product, for blowing apart dust deposits, and in particular for cleaning filter elements of dust-laden gas filtersxe2x80x94such as filter tubing, filter cartridges, filter candles, etc.xe2x80x94by back-washing, as is known, for example from Applicant""s EP 0 034 645 B1.
In the previously known Coanda injectors, the inlet of the pre-chamber is arranged laterally for the sake of simplicity so that the inlet of the pre-chamber and the inlet for the medium to be suctioned are essentially mutually perpendicular. The connection to the compressed gas line is thus not symmetrical. This means that the pressurized medium undergoes a plurality of changes in course when traveling the flow path from the compressed gas line into the inlet of the pre-chamber, through the pre-chamber, and finally to the nozzle slot. When a pressurized medium undergoes changes in course, especially at high flow rates, this causes substantial losses in pressure, which substantially reduce the efficiency of injectors and are associated with higher energy consumption. The non-symmetrical lateral arrangement of the inlet of the pre-chamber causes a plurality of changes in course in the pressure medium""s flow path, which is associated with substantial losses in pressure in the known Coanda injectors and thus reduces the efficiency of the Coanda injectors. In addition, the embodiments of the inlet of the pre-chamber known in the past are responsible for losses in pressure, which reduce efficiency, as does the conventional connecting means known in the past, e.g., tube fittings, bends, T-pieces, etc. In addition, in terms of construction, the non-symmetrical lateral arrangement of the inlet of the pre-chamber requires more space.
Given this prior art, the object of the invention is to improve a Coanda injector of the type specified in the foregoing, while avoiding the disadvantages described, such that a simple connection to a compressed gas line is possible that reduces losses in pressure and saves space.
The object is realized in accordance with the invention in that the inlet and the at least one inlet of the pre-chamber are arranged essentially in one plane so that the Coanda injector is directly connectable to the compressed gas line via the inlet of the pre-chamber.
Since the inlet of the pre-chamber is located essentially in one plane with the inlet for the medium to be suctioned, that is, in particular with only minor variations in the height, changes in course in the flow path that cause the losses in pressure are substantially reduced so that the Coanda injector in accordance with the invention has improved efficiency. In addition, the inventive configuration results in a simpler and more space-saving connection of the Coanda injector to the compressed gas line, in particular since the distance from the compressed gas line to the Coanda injector can be kept quite small.
In an advantageous embodiment of the invention, the pre-chamber is annular and surrounds the inlet for the medium to be suctioned. In a further embodiment, the pre-chamber has two mutually opposing inlets. This embodiment means the Coanda injector is centrally connectable in the direction of one of its center axes to the compressed gas line, which is associated with additional space-savings in terms of construction. In addition, the symmetrically arranged inlets of the pre-chamber improve the flow path and thus improve the efficiency of the Coanda injector in accordance with the invention.
In an additional advantageous embodiment of the invention, the inlet of the pre-chamber is provided with fluidically rounded members in the outflow region. The outflow region is primarily in the region on the flow path to the nozzle slot. The rounded members, which are embodied taking in account fluid dynamics, i.e. in a fluidic manner, prevent additional losses in pressure.
In accordance with a further advantageous embodiment of the invention, the nozzle slot is adjustable. This ensures that a defined nozzle slot required for the Coanda effect can be intentionally pre-specified. Advantageously, the pre-chamber also has an adjustable cover, which preferably has at least two spacing depressions for adjustment purposes, by means of which the height of the cover relative to the pre-chamber and therefore relative to the nozzle slot is adjustable. Advantageously, the inlet of the pre-chamber is arranged in the cover. This makes possible simple displacement of the cover without complex disassembly and assembly, especially since the inlet of the pre-chamber can be adjusted at the same time as the cover. Advantageously, the cover is joined in a gas-tight manner to the pre-chamber. There is a sufficient seal even without additional sealing means. However, additional sealing means can be used if this is required in order to reduce potential losses in pressure even further. For joining the cover to the pre-chamber, the latter is advantageously crimped around an upper edge. Of course other common connections can also be employed, such as bolts, rivets, welds, adhesives, clamps, and other connections, in particular so-called quarter-turn or bayonet fasteners. The Coanda injector is advantageously connected to the compressed gas line by welding. However, other connections can also be used.
In accordance with an additional particularly advantageous embodiment of the invention, the Coanda injector can be connected to the compressed gas line with at least one connecting member. This makes it possible to further simplify the connection, which furthermore makes possible an optimum, gas-tight connection in the manner of a material/material seal without using additional sealing materials.
Furthermore suggested with the present invention is a compressed gas line for connecting a Coanda injector in accordance with the invention, which compressed gas line is characterized in that it is provided fluidic chambers in the connection region of the inlet of the pre-chamber. This further reduces additional losses in pressure that are due to changes in course and connecting means that are unfavorable in terms of fluid mechanics.
In accordance with an additional advantageous embodiment of the invention, the compressed gas line is provided in the region of the inlet of the pre-chamber with flattened sections, whereby the connection plane to the cover then runs parallel and the disadvantages that are due to the different heights in the longitudinal and transverse directions as a result of the round cross-section of the connecting line are avoided.